German Patent Application No. 43 08 718, for example, describes that each of the two measuring chambers of a transducer measuring a pressure differential is filled through a filling channel after the respective measuring chamber has been evacuated. In filling each measuring chamber with the pressure transmission fluid, it is important to be sure that a defined volume of pressure transmission fluid be introduced into each measuring chamber. Each measuring chamber is gravity-filled with a pressure transmission fluid under vacuum. Then each filling channel is sealed by a sealing device which presses with a sealing ball on a ring lip on the outer end of the filling channel. The sealing ball is secured by a threaded pin.
Unexamined German Patent Application No. 20 38 868 describes another transducer measuring a pressure differential. For filling a measuring chamber with pressure transmission fluid, the pressure transmission fluid is filled into the measuring chamber under vacuum through a channel passing through a stopper after loosening a needle screw. With the help of the stopper, which can change positions due to its screwability and can be secured by a nut, the volume of the measuring chamber and thus the quantity of pressure transmission fluid can be adjusted.